Adjustable bicycle frame



FIG. 1 is a perspective view of an adjustable bicycle frame showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right side elevation view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is a rear elevation view thereof; and,

FIG. 7 is a front elevation view thereof. 

The ornamental design for an adjustable bicycle frame, as shown and described. 